The confidence interval is calculated as follows for
various values of a:

 x + taS, with n-l degrees of freedom


In the example there are (9-1) = 8 degrees
For a = 0.50 the value of t is 0.706 so
interval is 4.35  (0.706) (0.266) or from
t/ha.


of freedom.
the confidence
4.16 to 4.54


 All confidence intervals are calculated in the same
way. Fig. VII-6 shows the distribution of confidence
intervals of gross income for the improved system and the
traditional system. The traditional system is very stable
but at a much lower level of gross income. The same is
true of net income (Fig. VII-7). On the basis of these
two evaluation criteria, it would seem that the improved
system is definitely superior to the traditional system.




 50


 60 Traditional Maize in twin rows
 Maize with potatoes


 70
Confidence
Coefficient

 80



 90


 100
 0 1000 2000 3000

 Gross Income ($/ha)



FIG.VII-6. Distribution of confidence intervals for
 gross income, traditional maize versus maize
 in twin rows with potatoes.